Improvement in the purification of coal gas



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EMERSON MCMIL LIN, OF IRONTON, OHIO.

Letters Patent No. 100,309, (Ia-ted March 1, 1870.

IMPROVEMENT IN THE PURIFICATION OI COAL GAS,

The Schedule referred to in these Letters Patent and making part of the same To all whom it may concern Be it known that I, Emnasos MoMrnLm, of Iront0n,-in thecounty of Lawrence, and State of Ohio, have invented a new and improved Mode of Purifying Goal Gas for Illuminating Purposes; and I do hereby declare that the following is a full and exact descriptiouthereot', the same not admitting ot'illustration by drawings.

- The nature of my invention consists in removing the sulphur from coal gas by means of grindstone dust, and

in removing all the usual impurities fromcoal gas by employing gr'indstone dustin connection with dry lime.

- To enable others skilled in the art to use my inven- 'tion, I will proceed to describe the material which I employ, the mode of using it, and its action when so used.

The grindstonedust which I- use, is that obtained from. fiwtories where iron and steel tools or implements are ground. It is found in large quantities in such factories, and is at present a waste material having no commercial value. It consists, for the nrost'parr, of minute particles of iron and steel intimately mixed with silicicacid. It is generally found in clods or'aggregated lumps, and is of a brown color. In using this dust, I do not need any special apparatus, the forms of purifiers, 800., now in general use are suitable therefor. Since this dust does not absorb carbonic'acid, I use lime for that purpose, in theproport-ion of one-sixth in bulk of lim-e, to five-sixths of the dust.

\ The gas may be bronghtintoconfaet with the lime arrangement is to bring the gas first through thelii'ne,

so that any tar or naplr t-haline that may escape through the washer and condenser shall be arrested by the lime,

'and so not al lowed"to-pass into the 'grindstone dust,

which these impurities would render useless. If the gas be passed through array of loam, these impurities will be arrested andthelime 'rnaybe used in the up per tray. When the gas has passed through this material the usual time allowed for purifying with dry lime, the dust must-be removed and replaced by fresh dust. Tire dust is then of a black color, and is charged with iu'rpurities,,but it is not as otfensive as lime under sirnilarfcircumstances, and it can be handled and can be placed in heaps-without creating a nuisance.

, To restore its purifying qualities I pile it in a conical heap upon a core, so that itis abort one inch thick upon the core, and is thus exposed toThe action of the cessity of inventing any device.

atmosphere. In this position the dust mustnot get wet,'or it will not heat sufficiently, and the sulphur will not be driven oil, unless the weatherbe warm, but in dryweatlrer, 'and particularly when exposed to the direct rays of the sun, the dust heats, changes color from black to reddish,-and' is restored to its original qualities for purifying.- -Whether the dust be used for purifying, or be exposed to be itself restored, it must not be saturated with .water, but yet it must be moist, or it will not act or be acted on. When the dust is restored by .exposure to the atmosphere, it gradually loses its purifying qualities, unv til, after about six months use, it becomes comparatively inert. It is, however, fully restored to its active qualities by being exposed for a fewminutes toa red. heat in a retort, and this mode of restoration may apparently be employed to any extent desired, so that one supply of dust, allowance being made for'waste in handling, will last for anunlirnited time.

In large works I prefer-having two setsof purifiers, and having the lime in distinct. and separate. purifiers from thosein which the dust is used, so that one setnray be in use purifying gas, while the otherset is employed in restoring the dust that hasben used.-

Tire mode of doing this is to pass a current of hot air through the dust lying in the trays of the purifier,

which carries otf with it the sulphur and other ir'upur"-.

ities from the dust and changes its color from black to red, and so restores to itits purifying qualities By 'this meansall the expense of rehandling and removing the dust, together with the waste incident thereto, is saved, and the lime purifiers only would require cleaning out and recharging daily. When the dust has'been-pnrified in this way, it is quite dry, and conseq uently comparatively inert as a purifying agent. 'lo

moisten it, I pass a current of steam through it afterallowing it to cool, and the steam condensing-in the dust nroistens it, care being taken not to continue the dperati'on long enough to make the dnstwet.

The modepf sending the hot airorthe steam through the dust, does not need to be described as any gas engineercan arrange apparatus to do so without the ne- The puritying properties of this dust seem to depend partly upon its chemical constituents, partly upon its mechanical cornposition, and partly upon a galvanic actiou'developedlby the presenceof a metal and acid under the conditions of heat and moisture. The cheruical constituents are iron and silicic acid, with some unimportant additions.

The chemical action of iron, or its oxide, in purify ing gas, has .been long known, its strong afiinity for sulphur being its efficient property. But the action of silieic acid, either alone or in conjunction with iron, is not well known, yet it acts uponthegas i'eebly when alone, and powerfully in'connect-ion with iron, as in this dust. The mechanical compositionof this dust is the bestcalculated for exposing a large surface of the purifying agent to the action of the gas. 4 a H Both the iron and thesilicic acid are in the form of microscopic particles, which therefore have the maximum of surface exposed. to the gas, and which "yet' form a porous layer through which. gas can pass freely,

and which also are so intimately mixed that the particles ot' iron are kept apart and cannot cement to-.

gether as they absorb sulphur from the gas. Then the alternation of metallic particles, and acid particlesunder the conditions presented in a purifier, of heat and moisture, develops, a galvanic action throughout the oxide of iron in changing to the sulphate in the;

purifier, cakes together, and requires to be broken up before it can be used again after expelling the sulphur. 'lhen turnin'gs or-bon'ngs present so small an amount nfsnrihce'in proportion to the weightof the massused,

the interstices-between the pieces of iron are so large, that mnch of the gas escapes withoutcoming in contact with the iron; Further, both oxide of iron and pensive to get; They are also expensive in rehandling,

expense of rehandliug.

\Vhat I'claim as my 1nvention',and.desirc tosecure by Letters Patent, is as follows: I

fying coal gas for illuminating, by passing it through grindstone dust alone, c atter or before the gas has passed through dry 1ime. 7

used as often as. may be desired.

stone dust, for the purpose of purifying coal gas'for illuminating. a i

Witnesses: BENJAMIN GARVEY,

S. W. Monius.

that the use of them is attended with great labor. Also iron turnings have a commercial value, andare exs while 'grindstone dust is a waste material, having no commercial value, and is'easily used without the 1; The mode herein substantially described, of pu ri- 2. The mode herem substantially described, of restoring .the purifying properties of'grindstoue dust; after it has been used, so that it may be repeatedly T' 3. The employment, of any combination of iron and silicic acid, similar in-lts mechanical properties to grindjn. McMILLIK. 

